This document discusses quantitative inheritance, which refers to inheritance of traits that are influenced by multiple genes and the environment. Quantitative traits show continuous variation and are influenced by small effects from many genes. Examples discussed include human height, skin color, and kernel color in wheat. The kernel color experiment of Nilsson-Ehle is used to demonstrate quantitative inheritance. It involved crossing two wheat varieties and analyzing the ratios of kernel color phenotypes in the offspring. For the experiment to work well, the genes influencing color needed to have additive effects and the environment could not impact phenotypes. The experiment helped establish that quantitative traits are influenced by multiple independent gene loci.

1. QUANTITATIVE INHERITANCE
Arabinda Samanta
Assistant Professor in Botany
W.B.E.S
Jhargram Raj College
Govt. of West Bengal

2. Learning outcomes
• What is qualitative and quantitative characteristics.
• Concept of continuous and discontinuous variations.
• Physiology behind human skin colour.
• Understand quantitative inheritance with the example of human skin colour
and kernel colour of wheat
• Use of Pascal’s triangle in determining F2 phenotypic ratio in polygenic
inheritance.
• Problem solving in quantitative inheritance.

4. Arabinda Samanta
Assistant Professor
Dept. of Botany
Jhargram Raj College

5. Lets understand- what is Character
● Any observable feature, or trait, of an organism,
whether acquired or inherited (Brinicata.com)
● In the context of Genetics-Character could be
classified into two major groups
Quantitative Character Qualitative Character
Plant Yield, Grain Weight, Fruit
weight Plant height, Human
Body colour, IQ,
Eye colour in fruit fly, seed
colour, coat colour in animals,
disease like cystic fibrosis,
phenyl ketoneuria etc.

6. Qualitative
character
Monogenic character
Discontinuous variation
Less environmental variation
Polygenic character
Continuous variation
Strong environmental
variation
Quantitative
character

7. Quantitative
inheritance An
inheritance of a
character that depends
upon the cumulative
action of many genes,
each of which produces
only a small effect
Definition

8. Types of Quantitative Characteristics
Continuous characteristic
Meristic characteristics
Threshold characteristic
Human height
Not continuous, determined by multiple genetic and environmental factors
Although threshold characteristics exhibit only
two phenotypes, they are considered
quantitative because they, too are determined
by multiple genetic and environmental factors

9. What is your Height ?
● Human height is
controlled by polygene
● About 50 genes and
regions of the genome
have been associated
with height to date
● These genes act together
to produce a single
trait
● Higher the number of
genes involved, higher
the variation
● Expression of the genes
is cummulative in
nature.
Continuous characteristic

10. Some more polygenic characteristics

14. Lets learn about
human body colour
A, B and C each make equal
contributions to melanin
production while a, b and c
contribute nothing to melanin
production

16. Kernal Colour of wheat
Nilsson-Ehle’s cross

19. Pascal's triangle

20. First, genes affecting color segregated at only two or three loci. If genes at many
loci had been segregating, he would have had difficulty in distinguishing the
phenotypic classes.
Second, the genes affecting kernel color had strictly additive effects, making the
relation between genotype and phenotype simple.
Third, environment played almost no role in the phenotype; had environmental
factors modified the phenotypes, distinguishing between the five
phenotypic classes would have been difficult.
Finally, the loci that Nilsson-Ehle studied were not linked; so the genes
assorted independently
Comment on Nilsson-Ehle’s cross